In recent years, an infrared communication function is used for many devices. The infrared communication standards include an IrDA-D1.1 protocol (Infrared Data Association-Data ver1.1, hereafter referred to as IrDA protocol) and an IrSimple protocol, which was prescribed by IrDA in 2005 as a new communication standard (see page 63 to 68 on SHARP Technical Journal Vol. 95, February 2007).
Because the IrSimple protocol needs less time for connection and has much higher communication efficiency than a conventional IrDA protocol, the IrSimple protocol can reduce the time necessary for performing data communication of a certain size approximately by one-forth to one-tenth. In addition, the IrSimple protocol has two types of communication methods, that is, one-way communication and two-way communication, and can switch between the two depending on the purpose.
By using a device adopting the IrSimple protocol, for example, the following is possible: After a user takes a photo by using a cellular phone or a digital camera, the user can instantly transmit the photo to a television or a photo printer by operation as simple as a remote controller's operation. Thus, the IrSimple protocol is expected to be adopted in more applications as a new communication method.
The following explains an arrangement of a conventional transmitting device such as a portable terminal (such as a cellular phone, a PDA and the like); a digital camera; and the like, each of which corresponds to the infrared communication function using the IrSimple protocol. FIG. 12 is a block diagram schematically illustrating an arrangement of a conventional transmitting device.
A transmitting device 100 in FIG. 12 comprises a CPU 101, a communication controller 102, a transmitting section 103, a memory 104, a memory interface 105, an input section 106, and a ROM 107.
The CPU 101 is a means for controlling the transmitting device 100 by reading a control program (such as a protocol stack) from the ROM 107, and executing the control program. When the CPU 101 detects a transmission command from the input section 106, the CPU 101 reads out desired transmission data stored in the memory 104, converts the read data into the data compatible with the communication protocol, and requests the communication controller 102 to transmit the data.
When the communication controller 102 receives the transmission request from the CPU 101, the communication controller 102, based on the communication method, performs the data modulation on the protocol-converted data (the data converted to be compatible with the communication protocol). Then, the communication controller 102 outputs the modulated data to the transmitting section 103.
The transmitting section 103 is a means for transmitting the data which is outputted from the communication controller 102. For example, when infrared rays are used as a communication medium, the transmitting section 103 will be an LED (Light Emitting Diode) or an LD (Laser Diode), however, it is not limited to them. When other communication media are used, the transmitting section 103 will be the one which is suitable for the medium.
The memory 104 stores the data to be transmitted. The memory 104 may be a volatile memory (such as an SDRAM or the like) or a nonvolatile memory (such as a flash memory, an HDD, a DVD or the like). In FIG. 12, the memory 104 is positioned inside the transmitting device, but the memory 104 should not necessarily be inside the transmitting device. The memory 104 may be connected to the transmitting device as an external memory of the transmitting device.
The memory interface 105 has an interface function to the memory 104. For example, the memory interface 105 has an interface function for a USB, a memory card or the like. Through the memory interface 105, a user writes desired transmission data to the memory 104. The input section 106 is, for example, a transmission button or the like installed on the transmitting device 100. When the user presses the transmission button, the press of the button is detected and a transmission command is outputted to the CPU 101. The ROM 107 is a read-only program memory and stores a control program such as a protocol stack.
In the transmitting device 100 arranged as above, the CPU 101 and the communication controller 102 may be integrated into an application processor, thereby being one LSI.
Next, the following explains transmission procedures in the transmitting device 100. Firstly, the user requests from the input section 106 to transmit desired transmission data, for example, by pressing the transmission button. When the CPU 101 in the transmitting device detects the transmission request from the input section 106, the CPU 101 performs protocol conversion of the desired transmission data stored in the memory 104 which is in the transmitting device or is connected externally to the transmitting device. Thereby, the desired transmission data becomes compatible with the communication protocol. On the data whose protocol has been converted to be compatible with the communication protocol, the data modulation is performed by the communication controller 102 based on the communication method which the transmitting device adopts. Then, the transmission data is transmitted from the transmitting section 103.
As described above, in the conventional transmitting device 100, the CPU 101 performs the protocol conversion on the transmission data based on the communication protocols such as the IrSimple protocol. Then, based on the data modulating method which is compatible with the communication method such as the IrSimple communication method, the communication controller 102 modulates the transmission data whose protocol has been converted.
Next, a conversion sequence for transmission data in the conventional transmitting device is described below in reference to FIG. 13.
In the conventional transmitting device, desired transmission data (i.e., a transmission file) such as image data, text data and the like is normally written from an external device through the USB or memory card interface to the memory which is in the transmitting device or is connected externally to the transmitting device. When a transmission request from the user is received, on the transmission data which has been written to the memory, the protocol conversion is performed by the CPU, so that the transmission data is converted to be compatible with the communication protocol. The transmission data whose protocol has been converted is modulated by the communication controller based on the communication method. Then, the transmission data is transmitted from the transmitting section.
Other conventional technologies according to the present invention are as follows:    Japanese Unexamined Patent Application Publication, Tokukaihei, No. 2-285445 (published on Nov. 22, 1990)    IrDA Serial Infrared Link Access Protocol Specification for IrSimple Addition Version 1.0 (Oct. 14, 2005)    IrDA Serial Infrared Link Management Protocol Specification for IrSimple Addition Version 1.0 (Oct. 14, 2005)    IrDA Serial Infrared Sequence Management Protocol for IrSimple Version 1.0 (Oct. 14, 2005)    Infrared Data Association Object Exchange Protocol Version 1.3 (Jan. 3, 2003)
As described above, in the conventional transmitting devices such as: the portable terminal such as the cellular phone, the PDA and the like; the digital camera; and the like, the CPU and the communication controller in the transmitting device must perform the protocol conversion based on the communication protocol and the data modulation based on the communication method on desired transmission data. Therefore, the CPU and the communication controller are essential for the conventional transmitting devices.
That is, the CPU and the communication controller are essential even for a functionally-very-simple transmitting device (such as: a presentation data transmitting tool; a transmitting device for checking the operation of the receiving device which corresponds to the IrSimple; and the like, each of whose communication function can perform only the IrSimple one-way communication) that does not need to receive the data for the communication check from the communication recipient and that transmits the data stored in the memory located in the transmitting device. Therefore, there is a problem that the cost of the transmitting devices is very high.